Radio direction indicator



G. STAVIS RADIO DIRECTION INDICATOR Aug. 20, 1963 '4 Sheets-Sheet 1 INVENTOR GUS 57H V/5 ATTORNEY Aug. "zo, `19:53

G. sTAvls RADIO DIRECTION INDICATOR 4 Sheets--Sheei'I 2 Filed Feb. 4, 1950 Aug. 20, 1963 G. sTAvls RADIo DIRECTION INDICATOR 4 Sheets-Sheet 3 Filed Feb. 4, 1950 m u 0 C I, /V o f fn/,mf o E l M R C IM I ,a u m .il 2 i P l2 /.2 M f., E C m M n n o ,HI n II y. E x L D 9 D 9 2 5 A f 2 J 4 4 o4 4 rd l. L 3 L 4 2m 2 n n f. n n ro F N w a N N u/ s E M r M M n W w M m M m .ww L E T w en T O INVENTOR @Us am ws ATTORNEY Aug. 20, 1963 I G. sTAvls I v3,101,471

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UnitedStates Patent Oiiice 31,101,471 Patented Aug'. 20, 1963 3,101,471 RADIO DHRECTEN INDCATOR Gus Stavis, Ossining, NSY., assignor to International Standard Electric Corporation, New York, NY., a corporation of Delaware i Filled Feb. 4, 1950, Ser. No. 142,376 4 Claims. (Cl. 343-16) This invention relates to radio direction indicators and more particularly to direction indicators for indicating the position of a craft relative to a fixed course line.

`It is often desirable to indicate onthe ground the posi-` tion of la craft relative to a fixed course line, for the purpose of monitoring the craft position, control of traflic, directing the landing Iapproach of aircraft or for other purposes. With such systems it is essential that the equipmen be arranged to provide a minimum of obstruction at an airport, for example. Also it is helpful if such a system may be made to operate Without encumbering the craft with additional equipment. Obstruction may be provided by having antennas spaced apart on opposite sides of a runway or course line. However, at the higher operating radio frequencies such a Wide spacing results in an effective multi-lobe received pattern, which must be reduced 4in effective frequency so that an unambiguous indication is provided.

lSystems have been proposed wherein the direction of a craft from which pulses of energy are transmitted, either directly or by repeating or reflection of pulses from a ground station, is obtained by comparing the timing of pulses received at spaced antennas. Such systems might be adapted for the monitoring of aircraft, but they require particularly broad band equipment and special types of indicators. p

It is an object of the invention to provide a system for directional indication at a relatively lxed point, using FIG. 3 is a series of vector diagrams used in explaining the operation of the circuit of FIG. 2 and comprising a pair of spacediantennas 2 and 3 mounted on spaced receiving antennas and a circuit for converting More specifically the converted wavesrnay be combined to obtain a vectorial snm and diiference, one of these 'waves being shifted a further ninety degrees.

The-f separate sum and difference Waves are both modulated with separate indicating frequencies, one of these fre- One ofthe modulators is of the balanced type so that the carrier Wave is suppressed, while the output of the other includes the carrier. The outputs vof the modulators are then combined in a hydbrid network, this combined wave then being detected and the two modulatingfrequencies removed by filters. These removed modulating frequencies A:are then rectified and applied to a normal indicator such as used on aircraft.

While the general features of this invention have been described above a better understanding of these features and objects will be had from the particular description and embodiment thereof made with reference to the accompanying drawing in which:

FIG. l is a schematic diagram illustrating the general i opposed sides of the run-'way Three airplanes are shown at 4, 5 and 6, the airplane y4 being to the left of the runway, airplane 5 directly on course and airplane 6 to the right of the run-way. Antennas 2 and 3 are arranged to receive pulse signals `from any one of these airplanes. While the pulses might originate at the aircraft themselves, in the interest Ofmaintaining a minimum of equipment on the plane the pulses may be transmitted from the ground station by pulse transmitter 7. These transmitted pulses may be returned from the aircraft to the receiving antennas either by reflection or by repeating transponders carried by the aircraft as indicated at 8, `9 and 10 respectively. The received pulses are processed in the separate receivers r11 and 12 and applied to a course indicating comparator shown generally at 13. Associated With the landing equipment may be provided a glide path signal receiver and indicator shown generally at .14. The outputs from indicators .'13 and 14 may be combined if desired on a cross pointer .type of instrument similar to that normally carried by the aircraft.

. While it is not part of this invention the distance of the aircraft from the ground station may also be indicated by means of a `plan position indicator system shown at 15. This indicator system may be coupled to one of the receivers, 11.1 for example. Such a system may be similar to radar or distance measuring display systems synchronized with the pulses transmitted from 7. It 'will be seen that this entire system will provide an arrangement for monitoring the aircraft on the ground so that an indication similar to that provided on each craft may be observed on the ground.

Turning now to FIG. 2, a particular circuit arrangement which may be used in conjunction with antennas Z and 3 is shown. It will be observed that antennas 2 and 3 are spaced apart on opposite sides of the run-way. At the normal frequencies used for instrument landing or at higher frequencies these antennas will thus be spaced apart a plurality of 'wave lengths. the two antennas if combined will produce a multi-lobe pattern lwhich cannot be used to give a location without ambiguity. .Pulses from the antenna are received on the separate antennas 2 and 3 and a circuit .arrangement is provided for reducing the signals from the pulses to a wave energy of such a frequencythat the antennas are spaced apart la distance equal to half vvave length or less of this received energy. The phasing of the energy will, of course, be determined by the time difference at which the pulses are received at the two antennas. It will, `therefore, be seen that if this energy is combined cophasally from the antenna and also anti-phasally eectively two patterns overlapping in space midway between the antennas vvill be produced. This energy then may be applied to the course indicating comparator circuit 13 to give an indication of direction.

As shown each `o-f the receivers 11 and 12 comprises a first receiver arrangement 16, 17 which receives` the radio frequency pulses and `detects them to provide the envelope pulses. These envelope pulses are amplified. in video amplifiers 18, 19 and applied respectively to the Wave gen-` erat-ors or sub-carrier amplifiers 20, 21. It will be understood that the pulses coming from the airplane are Aof such repetition rate :and width as to favor the particular sub-carrier frequency to be selected. EachV of the subcarrier amplifiers 20, 21 is preferably provided with an Thus the energy received in cuit 13. This comparator circuit may include a bridge circuit 26`iconnected as a. hybrid coil. The input energ over line 25 is applied over transformer 27 so that the lenergy willV be Iin opposite phase at the terminals 'of the secondary thereof. The energy applied over line 24 is yapplied to transformer 28, the rsecondary of which lis coupled between the mid-point ofthe secondary of transformer 27 to ground so that this energy will be eophasal y Y applied to the `output terminals 29, tllof the secondary transformer 27. lt will thus be seen that the energy will add at one of the termin-als, 29 for example, iand subtract at the other` terminal 3i) providing in elfect'output energy combined in different phases vfrom the antennas 2 and 3. f t i For the purpose of providing an indication by means of instruments similar to those carried in the aircraft 2 indicating frequencies are generated. These may be generated -byvmeans of two simple resistance capacity oscillators 31and'32, the outputs of which are combined in mixer 33 to produce the desired tone frequencies,rof 90 and 150 cycles for example, which may be designated as F1 andFZ.. Filters 34 and 35 serve to separate these frequencies which may then be combined over a hybrid lcoil or 'other bridge network 36 to produce separate output tone frequencies. In output -line 37 for example the frequencies may be designated as Fl0, F20 while on line 38 the energy may be Fl0, and F2 180.

Energy from terminal 30 may be app-lied over a further p phase shifter 39 which produce an additional'90" phase shift to a modulator `40 together with thetone frequencies from line 37. l Modulator 40 is of the normal type providing the carrier frequency plus the two side bands. The energy from terminal 29 is applied to side band generator or balanced modulator 41 to which are applied the tone frequencies fromline 38 .so that at its output there appears only the side band energy. Output energies from modulators 40 and 41 are applied over terminals 42, 43

l .toanother hybrid coil or bridge circuit 44. It will be apparent that because ofthe phase difference of the subcarrier frequencies caused by the difference in timing of the pulses the tone frequencies F1 and F2 will combine in the bridge circuit 44 so their amplitudes will be varied fin accordance with the phase diiierence of the received I pulses.

Theoutput from hybrid coil 44 is applied to a `detector andlaudio amplifier 4S so that the different modulating tone frequency envelopes can be derived. The

rectifiers 48, 49 to an indicating meter 5 0.

The analysis of the operation of this circuit can be best understood by reference to the vector diagrams shown in FIG. 3. yAssuming the aircraft to be on course, the pulse which may be reiiected will arrive at antennas 2 and 3 simultaneously'so that thesub-carrier frequency appears in phase in lines 24 and 25. These need not be'of the` same magnitude although they preferably are but a ratio of 2-1 has been designated in the vector diagram to illustrate how the magnitude may vary. The output at the terminals 29 and 30 of the bridge are shown to be in phase.l After modulating the resulting phaseof the carrier and side band components at terminals 2 and 3 is shown. These are mixed and the resulting vector diagram l at the antenna 2 will lead that at antenna 3. The vector y posite side.

analysis shows that under these conditions the predominance `of the F2fcomponentwill produce the desired offcourse indication.` The vector analysis for the aircraft to the right `of the course shows a predominance of F1 modulation producing an olf-course indication to the optained land the indication will be the same as that produced ion an aircraft by a similartype of system.

It will be recognized that the only equipment necessary y ing it over a sector including tthe area to be monitored the display of the distance of the aircraft may alsoy be provi-dedif desired.

. at terminal 53 of the bridge 'and lin phase opposition at terminal 54 resulting in two output energies correspondy Turninglnow to FIG. 4, inthisl arrangement the antennas 2 and 3 and receivers 11Vand -12are the same as those shown in FIG. 2. However,rthe comparator circuit is of somewhat simpler form. The energy applied from lines 24, 25. is supplied to the vtransmission line bridge networkl shown conventionallyfin single line diagram.` IIn one-arm of the bridge Slis provided transposition'y 52. It will be seen that the enengy over line 25 will be combined cophasally with the energy over line 24 ing to Ithe'sum and diiference respectivelyof the energy from the receivers 11 and 12. These energies after one of them has been shifted in phase in shift 39 are applied in diagonally opposed terminals of a bridge network-55 similar to network 51. i This bridge alsorhas av transportation shown-at 56. Thus these wave energies Vare added at a terminal 57 and subtracted at termina-l 58. The output energy from these terminals is then modulated by f modulators 59 and 60 respectively, which modulators may modulating tone frequencies froml detector amplifier 45 g are applied over` respective lters 46, 47 and individual be of the mechanical or electronicA type normally used in radio beacons.v These modulated energies are then 'l combined-over a third bridge network 61 in additive relation so that at output terminal 62 their sum will appear.

The diagonally opposed terminal 63 of the bridge isconnected to a dis-sipating resistor 64. However, as the carrier energy -is transposed at transposition 65 theV amount of energy to be dissipated` will be `lessfthanthat at the output terminal. vEnergy from terminall 62 is applied' to a detector'63 andanaudio ampliier 64 and hence over lters 46, 47` and rectitiers 48 and 49 to the indicating lmeterSll. y -Whifle only two modications lof this invention have been ydisclosed it is clear that many changes may be made without `departing from the scope thereof.l ln place of the various transmission vline bridge networks various forms of hybrid coil networks may be used. Furthermore, many other variations will readily vpresent them'.- selvesto those skilled in the art.

While I have described abovel the principles of my in-V ventionl in connection'with specific apparatus, it is to be clearly understood that this description is made only by way of example and not fas a limitation to my invention. 1

What I claim is: I y

f 1. An indicating system for indicating the position of a the scopev of l craft at la relatively fixed station in response to electrical pulses received from said craft 'at spaced points at said vrelatively iixed station, comprising a pair of spaced receiving antennas, la translator means for deriving from said. received pulses `at each antenna, wave energies of a frequencysuch that a half wave thereof is at least equaly to` said antenna spacing andphasecl with respect to each other dependent upon the time of reception of said lantennas, combining means comprising means for deriving waves equal to a vector sum and a vector diterence of i v Thu-s the normal localiser operation is ob-v the Wave energy from said translator means and a phase shifter for one of the combined derived Waves to produce a ninety degree phase shift thereof, to derive different Waves therefrom, means for differently lmodulating said different waves and meansresponsive to said different modulated Waves lto produce a directive indication of the location of said craft.

2. An indicating system for indicating the position of a craft at 'a relatively iixed station in response to pulses of radio frequency energy from said craft received at spaced points at said relatively :fixed station comprising a pair of antennas spaced apart a plurality of wavelengths at said radio frequency, lmeans for detecting said Waves to produce envelope pulses, Itranslator means for deriving from said envelope pulses at each antenna wave energy of Ia frequency such that a half Wave thereof is at least equal to the antenna spacing of said pair and phased With respect to one another dependent upon the 'time of reception :of said pulses by said antennas, combining means comprising means for deriving Waves equal -to a vector sum yand a vector diiference of the Wave energy from said translator means and a phase shifter for one of the combined derived Waves toproduce `a ninety degree phase shift thereof, to derive different Waves therefrom, means for modulating diiferently said different Waves, and means responsive to said differently modulated Waves to produce a directive indication of the source of said received energy. p

3. An indicating system according to claim 2, wherein said means for differently modulating said waves comprises a source of iitst and second indicator energies of different frequencies, a carrier output modulator and la balanced modulator, means for applying said derived Waves to respective ones of said modulators, means for applying said first and second indicator energies cophasally to one of said modulators and means for applying said first yand second indicator energies antiphasally to the other of said'modulators.

v4. An indicator system 'according to claim 3 wherein said means responsive to said differently modulated Waves, comprises a hybrid network vfor combining said differently modulated Waves, .a detector for deriving said indicator Wave component-s from said combined Waves, means for separating said components, means for rectifying said separated components and a meter to indicate direction in response to said rectified components.

References Cited in the le of this patent UNITED STATES PATENTS 2,216,708 Kolster Oct. 1, 1940 2,476,977 Hansel July 26, 1949 2,479,892 Aicardi Aug. 23, 1949 2,495,718 Hardy Jan. 31, 1950 2,514,351 Smith July 4, 1950I 2,528,141 Hastings Oct. 31, 1950 FOREIGN PATENTS 586,278 Great Britain Mar. 13, 1947 

1. AN INDICATING SYSTEM FOR INDICATING POSITION OF A CRAFT AT A RELATIVELY FIXED STATION IN RESPONSE TO ELECTRICAL PULSES RECEIVED FROM SAID CRAFT AT SPACED POINTS AT SAID RELATIVELY FIXED STATION, COMPRISING A PAIR OF SPACED RECEIVING ANTENNAS, A TRANSLATOR MEANS FOR DERIVING FROM SAID RECEIVED PULSES AT EACH ANTENNA, WAVE ENERGIES OF A FREQUENCY SUCH THAT A HALF WAVE THEREOF IS AT LEAST EQUAL TO SAID ANTENNA SPACING AND PHASED WITH RESPECT TO EACH OTHER, DEPENDENT UPON THE TIME OF RECEPTION OF SAID ANTENNAS, COMBINING MEANS COMPRISING MEANS FOR DERIVING 